ANTI-VIBRATION GRINDING DEVICE WITH HUB AND SPRING

Abstract

A grinding device including a grinding wheel, a hub attached to the grinding wheel, the hub movable relative to the grinding wheel in an axial direction of the hub.

Claims

1. A grinding device, comprising: a grinding wheel; a hub attached to the grinding wheel, the hub movable relative to the grinding wheel in an axial direction of the hub.

2. The grinding device of claim 1, wherein the hub comprises a top flange, a bottom flange and a body extending between the top flange and bottom flange.

3. The grinding device of claim 2, wherein the hub is biased downwardly with respect to the hub.

4. The grinding device of claim 2, further comprising a spring between the top flange and a top surface of the grinding wheel.

5. The grinding device of claim 4, wherein spring is a wave spring.

6. The grinding device of claim 1, further comprising an abrasive surface on a bottom surface of the grinding wheel.

7. The grinding device of claim 2, wherein the hub comprises a bolt forming the top flange and body and a nut forming the bottom flange releasably connected to the bolt.

8. The grinding device of claim 7, wherein the bolt has external threads mating with internal threads of the nut.

9. The grinding device of claim 8, wherein the bolt has internal threads configured to mate with a power tool.

10. The grinding device of claim 1, wherein the hub is biased downwardly with respect to the hub by a bias member, and wherein a top end of the bias member is fixed with respect to the hub and a bottom end of the bias member bears against the grinding wheel.

11. The grinding device of claim 1, wherein the bias member is a wave spring.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0005] FIG. 1 is a top perspective view of the grinding device;

[0006] FIG. 2 is a bottom perspective view of the grinding device;

[0007] FIG. 3 is an exploded view of the grinding device;

[0008] FIG. 4 is a top view of the grinding device;

[0009] FIG. 5 is a top view of the bottom flange of the hub;

[0010] FIG. 6 is an exploded view of the hub;

[0011] FIG. 7 is an isometric view of the top and bottom hubs unattached; and

[0012] FIG. 8 is a chart of examples of the data with maximum and minimum values for all x, y, and z directions.

DETAILED DESCRIPTION OF THE INVENTION

[0013] FIG. 1 depicts the grinding device 10 having a hub 12 and grinding wheel 20. The hub attaches to an arbor or spindle of a power tool and rotates the grinding wheel 20. The grinding wheel has a central dome portion 22 and an outwardly extending rim 24. The concavity formed by the central dome portion creates a space for the bottom of the flange to be under the grinding wheel but not interfere with the grinding wheel's contact with the workpiece. As can be seen in the bottom view of FIG. 2, the hub 12 extends through the grinding wheel so that the hub is attached to the grinding wheel, as will be explained in more detail. A bottom surface of the grinding wheel has an abrasive surface 26. The abrasive surface may be any suitable abrasive surface, such as a diamond abrasive surface. The grinding wheel is biased downwardly relative to the hub by any suitable means such as a damper, a wave spring, a coil spring or a Belleville spring. The biasing device preferably encircles the hub and extends between a top flange of the hub 12 and a top surface of the grinding wheel.

[0014] As shown in FIG. 3, the hub has a top flange 14 and a bottom flange 18. A body 16 of the hub extends between the top flange and bottom flange and through an aperture in the grinding wheel. The body of the hub is longer than a thickness of the plate forming the grinding wheel, allowing the hub 12 to move relative to the grinding wheel 20. A spring 30 bears against the bottom surface of the top flange 14 and a top surface of the grinding wheel. While the hub 12 can move relative to the grinding wheel 20, the spring 30 forces the grinding wheel against the bottom flange 18.

[0015] FIG. 3 also demonstrates how the hub 12 is attached to the grinding wheel 30. The bottom flange 18 may be a nut that releasable connects to a bolt forming the body 16 and top flange 14 of the hub. The nut can be attached to the bolt and the bolt can be attached to the arbor or spindle by any suitable means, such as mating threads. For example, male threads on the bottom of the bolt can be attached to female threads on the nut and female threads on the bolt can attach to the arbor or spindle, as will be explained later.

[0016] The hub 12 can be keyed to the grinding wheel 20 to impart rotational motion of the hub, as driven by the arbor or spindle, to the grinding wheel. The hub body may have a polygonal cross sectional shape, such as hexagonal or octagonal, with the aperture in the grinding wheel having a corresponding shape. Another way to key the hub to the grinding wheel is to provide projections on the upper surface of the bottom flange which fit into extensions in the aperture of the grinding wheel, as will be described later.

[0017] To assemble the hub onto the grinding wheel, the projection are aligned with and placed into the extensions of the aperture from the bottom surface of the grinding wheel. A spring fits about the body of the hub then the threads 36 in FIG. 6 would be screwed down to threads of the bottom hub 18. The spring would be fixed between head of the top hub 14 and the grinding device 20 as shown in FIG. 2.

[0018] FIG. 4 clearly depicts the central aperture 28 of the grinding wheel having a main aperture for receiving the body of the hub and two extensions receiving the projections of the bottom flange of the hub. FIG. 5 depicts the top surface of the bottom flange 18. The projections 32 extend upwardly from the top surface. The size and shape of the projections 32 are complimentary to the extensions of the central aperture in the grinding wheel to prevent relative rotation between the hub and grinding wheel. Therefore, when the hub drives the grinding wheel when driven by a suitable device, such as a power tool.

[0019] FIGS. 6 and 7 depict one possible construction of the hub. A bolt forms the top flange 14 and body 16 of the hub. The bottom flange 18 is formed by a nut and joins to the bolt by having internal threads 34 mate which with external threads 36 of the bolt. The top of the bolt has internal threads 38 to attach to a spindle or arbor of a power tool.

[0020] In order to perform a vibration test, four of the same types of grinding wheels were prepared but with different hubs. The first two grinding wheel samples had regular fixed hub. For the other two grinding wheel samples, the invention hubs with spring were mounted. The samples were then balanced on balancing machines accordingly. After the preparation, the vibration was tested by using a vibration meter attached to an angle grinder with a sample grinding wheel mounted on. A tester then turns on the angle grinder and firmly grind a material surface for certain time. The same tests were performed for all grinding wheel samples. The vibration meter provides acceleration values for x, y, and z directions in m/s.sup.2 for each test. The lower values in each direction mean less vibration impacted on the angle grinder in each direction. The chart below provides average acceleration in each direction for each of the four different tests.

[0021] The ability of the grinding wheel to move relative to the hub allows for lower vibration.

TABLE-US-00001 Conventional Grinding Device Grinding Device with Biased Hub Balancing X Y Z Total X Y Z Total 2.5 g/mm 11.512 16.242 19.688 27.999 9.3482 11.985 20.132 25.226 60 g/mm 11.611 27.995 59.209 66.515 9.4881 12.486 24.736 29.288
The above result shows that if the grinding devices are not properly balanced (2.sup.nd row results on the table), the one with the invention dampens the vibration more. Even though the grinding devices are well balanced (1.sup.st row results on the table), the one with the invention provided lower vibration result.
The charts of FIG. 8 are examples of the data with maximum and minimum values for all x, y, and z directions for 2.5 g/mm balanced samples. As shown on the chart, even for the well balanced grinding wheel samples, the maximum acceleration values for the grinding wheels with the invention are about 15% lower in average.
The invention thus being described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims.